No, this has nothing to do with porn.
A finisher is usually something you do at the end of a training session that involves a lot of reps or work over a short period of time. I'm going to list some finishers I've used over the years.
Pecs - 100+ rep drop sets on pec-deck - Back in my teens we used to do this one after all of our pressing work. We'd shoot for 10-12 reps on the first set, then drop the pin on the stack to something lighter and shoot for 20-30 reps on the second set. Once again we'd drop the weight and shoot for something like 50-60 reps on the last set. We'd try to get 100+ reps over the three "sets" but sometimes it would require a 3rd strip set.
Press Behind the neck - 65 pounds - 6 sets of 12 reps with 60 seconds between sets - Doesn't sound like shit does it? Try it. After all of the previous shoulder work this would be hard as fuck.
Giant set side laterals - 20-15-10 reps - then 10-15-25 reps. Grab a light pair of db's and do 25 reps. Then a heavier pair and do 15, then a heavier pair and do 10. Rest 3 minutes and then repeat the whole sequence using the same db's. But this time, 10-15-25.
Leg Press - 25-50-75-100 - This I only did a few times because it was fucking awful. You need a couple of people to train with to do it correctly IMO. Do a set of 25, then have the other people strip off a few plates. Do 50, and repeat. Do 75 and repeat. Then do 100 to finish. It was fucking brutally awful and I would be sore for a week after.
Walking lunges for 15 minutes - You better be in pretty good condition for this one. Yeah, you'll have to stop a lot and don't worry about counting reps. Just do as many as you can for the entire 15 minutes.
100 rep donkey calf raises - You don't need some dudes riding on your back for these, and I promise you won't want that anyway. Again. Just get the reps in. Let me give a word of advice here. Don't do this right out of the gate if you haven't been doing calf work. Go for 40 the first time or so. I will tell you why. My calves got so sore from these the first time I did them that I couldn't straight my legs the next few days after. I literally walked with a cane. If you think I'm kidding, be stupid like I was and do it. See what happens.
100 rep plate raises - Grab a 25 pound plate and do 100 reps non stop. Pretty simple. Right?
Bench Dips to failure with rest/pause - Dips between benches, do as many as you can, then take a break for 30 seconds, and go again. Repeat one more time for as many as you can.
T-bar rows - crazy 8's - 8 sets of 8 reps non-stop. You will need to use smaller plates here. Do a set of 8, strip off some weight, do 8, then keep repeating until a total of 8 "sets" are done.
Most finishers involve some sort of intensity technique like giant, strip, or rest/pause sets. These are all ways to extend the set past just going to failure. I am not a fan of forced reps for many reasons. I that for most guys form breaks down too much during those, and because the amount of assistance given from the spotter can vary greatly.
Some of these, like the side laterals or 100 rep plate raises, can be done on a weekly basis with no problem. Things done for legs and back shouldn't be done quite as often. But you'll figure that out once you try them.
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Good stuff as always. On an unrelated note, thanks also for posting the link to the LRB Facebook page. I don't have one myself and it makes it a little more convenient for me to check your posts there as well.
Good luck with the meet prep.